Direct numerical simulations of incompressible nonhelical randomly forced MHD turbulence are used to demonstrate for the first time that the fluctuation dynamo exists in the limit of large magnetic Reynolds number $\mathrm{Rm}\gg 1$ and small magnetic Prandtl number $\mathrm{Pm}\ll 1$. The dependence of the critical ${\mathrm{Rm}}_c$ for dynamo on the hydrodynamic Reynolds number Re is obtained for $1\lesssim \mathrm{Re}\lesssim 6700$. In the limit $\mathrm{Pm}\ll 1$, ${\mathrm{Rm}}_c$ is about 3 times larger than for the previously well-established dynamo at large and moderate Prandtl numbers: ${\mathrm{Rm}}_c\lesssim 200$ for $\mathrm{Re}\gtrsim 6000$ compared to ${\mathrm{Rm}}_c\sim 60$ for $\mathrm{Pm}\ge 1$. It is not yet possible to determine numerically whether the growth rate of the magnetic energy is $\propto {\mathrm{Rm}}^{1/2}$ in the limit $\mathrm{Rm}\to \infty$, as it should be if the dynamo is driven by the inertial-range motions at the resistive scale.

The feasibility of a mean-field dynamo in nonhelical turbulence with a superimposed linear shear is studied numerically in elongated shearing boxes. Exponential growth of the magnetic field at scales much larger than the outer scale of the turbulence is found. The characteristic scale of the field is $l_{\overline{B}}\propto S^{-1/2}$ and the growth rate is $\gamma \propto S$, where $S$ is the shearing rate. This newly discovered shear dynamo effect potentially represents a very generic mechanism for generating large-scale magnetic fields in a broad class of astrophysical systems with spatially coherent mean flows.

Femtosecond laser-produced plasmas are bright ultrafast line x-ray sources potentially suitable for different applications including material science and biology. The conversion efficiency of the laser energy incident onto a solid target into the x-ray emission is significantly enhanced when a laser prepulse precedes the main pulse. The details of x-ray line emission from solid targets irradiated by a pair of ultrashort laser pulses are investigated both theoretically and experimentally. Insight into spatial and temporal characteristics of the line x-ray source is provided by numerical simulations and a simplified analytical model. Optimal time separation of the laser pulses is searched for in order to reach the maximum conversion of laser energy into the emission of selected x-ray lines. We deduced how the optimal pulse separation scales with laser and target parameters.